They USUALLY make plenty of sense. My dad is a CFO, so he should know how money works? I think? I really don't know what's going on with this.
He's making choices that seem sensible to him, based on things that either you don't know or that he considers important and you don't.
It happens all the time--different people consider different things when making choices. It's not just parents/children, either. I know plenty of adults that make choices in different ways, and disagree about what's "best."